Abstract:Fire disturbance is one of the important factors affecting the structure and function of forest soil ecosystem. In order to provide theoretical guidance for forest regeneration and sustainable management after fire disturbance, this study explored the dynamic characteristics of physiochemical properties in forest soil after different fire disturbances. The effects of fire intensities (control, low, moderate and high intensity fire) and time nodes (3, 30, 180, 360, 720 days after fire) on bulk density (BD), soil water repellency (SWR), soil organic matter (SOM), pH, total nitrogen (TN), total phosphorus (TP) and total potassium (TK) contents were measured in a field-scale experiment with 16 plots (20 m×20 m) from Liquidambar formosana secondary forests in Zhuzhou, Hunan Province, China from 2014 to 2016. The differences and changing trends of soil properties among different fire disturbances at the same time node and different time nodes under the same fire disturbance were studied by descriptive statistical analysis, one way ANOVA and Fisher LSD test (p<0.05). The result showed that BD, SWR, pH, and TK increased with the increase of fire intensities, while SOM and TP decreased after the fire disturbance at the same time node. There was no significant difference of TN among different fire disturbances. Compared with the control, the effects of low intensity fire on BD, SWR, pH and SOM were not significant at the same time node, the effects of moderate intensity fire on these soil physiochemical properties were significant at some time nodes, while the effects of high intensity fire on them were significant. After the same intensity of fire disturbance, there were significant differences in BD, SWR and pH among different time nodes (p<0.05). BD, SWR and pH increased significantly at the first three days after fire, then decreased gradually; BD returned to pre-fire level after 360 days of fire, while SWR and pH needed 720 days after fire. However, there were significant differences of SOM between 360, 720 days and other time nodes only after high intensity fire. After fire disturbance, SOM decreased first, then increased gradually, and returned to the level before fire and maintained stability after 360 days. After fire with moderate and high intensities, the greater the time span was, the more significant the difference of TK was, while the differences of TN, TP were only significant after high intensity fire. Fire intensities and time nodes had certain effects on the studied soil properties, among which high intensity fire showed the biggest effects on soil properties. Fire disturbance caused soil fertility decline in the short time and affected the soil nutrient status of forest land. However, with the time went on, the properties of soil physiochemical gradually recovered to the pre-fire level after two years.